Thanks Steve and Felix - you have sent me down the path to solving my problem. Andy Steve Ratcliffe wrote:
Hi
I understand how to solve this problem (osmosis, osmcut, etc.) but I'm wondering what the size limit is and whether it is imposed by the IMG file format or mkgmap. Does anyone know?
The limit is in the IMG format, or at least the version of the format that we know how to use. It is not the size of the file as a whole but of one section within it. Files containing routing information for example will be much bigger in total size.
The default style is somewhat heavyweight as it contains all residential roads on two different zoom levels. You would get about twice the amount with a less heavy style. (You could try --levels='0:23,1:21,2:19' for a rough idea).
All garmin maps commercial or otherwise are split into tiles. In the days before cheap SD cards it would have been a necessary feature that the map was split into small enough chunks that you could load a few sections you were interested in onto limited memory.
..Steve
-- Andy PGP Key ID: 0xDC1B5864